Power hammer



.June 24, 19M. D. v. AcKz-:RMAN

POWER HAMMER Filed March 13, 1937 2 Sheets-Sheet l Inv@ nim.

.Wue 24, 194W. D. v. ACKERMAN POWER HAMMER Filed March 13, 1957 2 Sheets-Sheet 2 [mwen/ion 17a vid' Vf/ckermqn.

Patented June 24, 1941 ateosI UNITEDSTATES PATENT oFFlcs David V. Ackerman, San Francisco, Calif., as-

sgnor of one-half to Henri H. Cloutier, Seattle,

Wash.

Application March 13, 1937, Serial No. 130,768 i 6 Claims.

This invention has to do generally` with power hammers and is more particularly concerned with hammers of the mechanical type wherein reciprocation is accomplished `by arotary cam or eccentric. Such hammers are useful in hard rock drilling, pavement breaking, paint chipping, and other similar operations, though in no way limited to such use.

Among the purposes of the invention is the provision of a simple, sturdy and easily operated hammer which is capable of delivering forceful blows in rapid succession with a minimum expenditure of power. I I

There is also provided a novel adjustment means whereby it is placed within the power of the operator to varyI at will the stroke `of the hammer and hence control 'the forcefulness of the blows. This adjustment is constantly within the control of the operator, irrespective of the rapidity with which the blows are being struck, and is of a nature to enable him to vary the blows, either :gradually or abruptly, from the lightest tap to full power by merely exerting hand-pressure on a control lever. Preferably,A the adjustment is such that `when the control yleveris released, the adjustment automatically is put in such condition that the actuating cam rotates idly, so the operation of the cam-rotating means need not be `interrupted and yet reciprocation of the hammer element ceases.

As a particular feature, I have incorporated in the hammer a slip cam of the type illustrated and broadly claimed in my copending application entitled Adjustable slip cam, filed May 10, 1935 under Serial Number 20,740, now` Patent No. 2,183,950, and I have herein claimed certainfeatures of that novel mechanical movement in combination with elements of the hammer.

Other objects and features of the invention will be made apparent in the following detailed description, reference being had 'to the accompanying drawings, in which:

Figure 1 shows a medial section taken through the body of a hammer embodying my invention, certain elements contained therein being shown in elevation. I

, Fig. 2 is a side elevation of Fig. 1, the upper part of the body being shown in section as it appears along line 2-2 of Fig. l.

Figs. 3 to 7, inclusive, are diagrammatic views showing the relative positions of parts during different stages of operation. I

For purposes of easy assembly,V the body or supporting structure I` is sectional, being made up of camhousing II to which a side plate I2 is bolted at I3; tubular hammer-housing I4 being threadably connected to cam housing II at I5.

A cylindrical hammer or striker I6 is mounted for vertical reciprocation in housing I4, being guided or centered in its movement by the inte gral flange I1 which slidingly ts housing bore I8, and abutment ring I9 which is threaded into the upper end of housing I4, and whose bore slidingly takes hammer I5. I

Compression spring 20 is interposed between ring I9 and ange `I'I and tends always to urge hammer or striker I6 downwardly into contact with an anvil. This anvil may be considered either the upwardly facing shoulder 2l ofhousing I4, which shoulder is adapted to be contacted .by the underface of flange I'I, or the upper end.

22 of shank 23 of percussion tool 2d; or, if the proportions are such that flange II and the end A25 of hammer I6 strike shoulder 2I and end 22 simultaneously, said shoulder and end may together be considered as the anvil.

Shank 23 of tool 24 fits within bushing 26, the latter fitting withinthe lower and reduced-diameter portion 21 of bore I 8. Bushing fiange `28 ts up against the lower end of housing I4, while tool-liange 29 engages the underside of flange 2B.

Horizontal drive shaft 30 extends across the hollow 3| of housing II, being journaled in housing-supported bearings 32. While the shaft ymay be powered in any suitable manner, I have herein shown, by way of example only, a flexible power shaft 33 applied thereto.

A slip cam in the form of a disk 3d is positioned within hollow 3i, and broadly considered, it is so associated with shaft `3Il that it is adapted to be rotated thereby and, while being so rotated, to slide radially with respect to the shaft under prescribed conditions, whereby the disk may move to and from a position Where its center of vsymmetry coincides with its axis of rotation (in this case that axis coinciding with the shaft axis) or whereby its center of symmetry may be located at varying distances from its axis of rotation to vary the degree of eccentricity of the cam.

Without intending to limit the invention, considered in its broader aspects, by the specific showing herein, `I have illustrated this association as brought about by radially slottingthe disk at 35 and 'extending a squared portion 36 of shaft 30 through this slot. The squared portion fits the slot across its transverse axis so rotation cf the shaft rotates the disk, while the longitudinal extent of the slot is of an extent to allow coincident sliding movement of the disk with relation to the shaft under vcertain conditions. Though this is not limitative on the invention considered in its broader aspects, slot 35 preferably extends diametrically a sufficient distance each side of the center to allow the disk to slide in opposite directions to points where its center of Symmetry A is at either side of its axis of rotation B, the advantage of this feature being pointed out later.

Hammer I6 has a yoke extension 31, the arms 38 of which extend upwardly along opposite sides of the disk, though they are out back at 39 to avoid interference with shaft 3o. Washers 4|] on shaft 30 may be interposed between the arms and the cam to center the latter. Roller 4| is mounted on shaft 42 which is extended between the upper ends of arms 38, said roller being adapted, at times, to engage the peripheral face 43 of disk 34 near the top thereof. While the roller, which may be broadly considered as a transversely extending portion or element of hammer I6, is illustrated as disposed directly over the center of hammer I6, preferably it is offset with relation to the vertical axial plane C-C of shaft 3i), whereby the slip-action of the cam is improved, as will appear.

For purposes of reference the hammer is spoken of as vertically reciprocable, the shaft is said to be horizontal, and the roller is spoken of as being near the top of the disk, but where these descriptive designations are included in the claims they are not to be considered as limitative except as to relationship, for obviously the device can, for instance, be held in a horizontal position, in which case the hammer would reciprocate horizontally and the roller would be at the side of the disk, and yet such an arrangement (whether permanent or merely due to tipping up a normally vertical hammer) would clearly come within the scope of the invention and is intended to comeY within the scope of the claims.

An adjustable stop member or shoe 44 is disposed within housing at a point substantially diametrically opposite roller 4| and this member, though it is actually mounted for reciprocation in a direction parallel to plane C-C or to the axis of hammer I6, is movable, in effect, towards and away from shaft 30 or, in other words, towards and away from axis of rotation B of disk 34.

While not limitative on the broader aspects of the invention, shoe 44 is here shown of arcuate shape, and, for purposes of reference, the opposite ends will be termed a heel 45 and toe 45.

Shoe 44 is supported on support rod or plunger 41 adapted to play through housing-socket 48, while thrust rod 49 extends upwardly along one side of disk 34 into lost-motion, pivotal connection at 54 with a control lever 5| which is centrally pivoted at to housing Preferably, control lever or trigger 5| is disposed immediately beneath one of the handles 52 by which the hammer is bodily manipulated. Accordingly, lever 5| may be operated by squeezing pressure of the operators hand.

Compression spring 53 is interposed between:

the underside of shoe 44 and the upwardly facing shoulder 54 of housing Il, thus tending to urge the shoe upwardly. Downwardly facing shoulder 55 of housing serves as a stop to limit counterclockwise rotation (Fig. 1) oflever 5| and hence upward movement of thrust rod 49 and shoe 44, the relative positions and proportions of parts being such that spring 53, in yieldably holding shoe 44 at its upward limit, normally maintains said stop and hence disk 34 in such positions that the axis of symmetry A and axis of rotation B coincide. It follows that in this normal or inoperative condition (Fig. 1) shaft rotation merely causes concentric disk-rotation and no impulses are imparted to hammer I l.

Assume now that, with the parts in the position of Fig. 1 shaft 30 is stationary but that lever 5| is actuated to thrust shoe 44 down to its limit (as established, for instance, either by plunger 41 striking the bottom of socket 48 or by lever 5| striking housing shoulder 5S). Disk 34 will then slide down by gravity, following shoe 44 to its lowermost position. As shaft 30 and hence disk 34 are rotated in a counterclockwise direction (as viewed in Fig. 1) when slot 35 reaches a vertical position, disk 34 will have dropped to the position of Fig. 3, wherein the center of symmetry A of the disk is disposed at one side of axis of rotation B, so the disk now has the characteristics of an eccentric, and it is well below roller 4|.

As rotation of disk 34 (now effective as an eccentric or cam) is continued, it contacts roller 4| (Fig. 4) though the disk, in its angular move ment from the position of Fig. 3 to that of Fig. 4, may have been pushed radially inward a short distance by its passage over the toe end 45 of the shoe. However, the extent cf such inward thrust, if it occurs, is negligible.

During further rotation of the disk from the position of Fig. 4 to that of Fig. 5, it acts eccentrically to lift hammer I6 against the force of power spring 2|). The load, as here represented by the force exerted by spring 20, is transmitted to the disk through hammer |6 and roller 4|, and while it moves vertically on a line somewhat offset from a radial line through the disk, the load force exerted on the disk by the roller is substantially radially of the cam.

When the line of cam slip (the longitudinal axis of slot 35) approaches the line of force of the load (a position at or approaching that of Fig. 5) the cam suddenly slips or is projected diametrically to the position of Fig. 6, thus freeing the hammer for sudden downward movement under the impulse of spring 20, whereupon it delivers its blow on the underlying anvil.

Now the exact position of the cam when its slips (angular position of the cam with reference to the line of load force) depends, among other things, on the friction that opposes the sliding of the cam on the shaft. If the friction between the two is relatively large the cam will reach substantially the position of Fig. 6 before slipping; if relatively small, the cam will slip an earlier stage in its angular movement; but the cam cannot slip until the axis of its slot 35 has passed beyond a position at right angles to the line of the load force and consequently must always lift the load and the subsequent cam-slip must always lower the load.

When the cam slips or is thus forcibly projected towards the position of Fig. 6, it impacts and is checked by the heel portion 45 of shoe 44, slot 35 being of such length that even when the shoe is in its lowermost position there will be clearance between shaft 36 and the upper end of this slot. It follows that all the cam-checking force is taken by the shoe and none is transmitted to the shaft, an obvious advantage.

As long as lever 5| is held in a manner to retain shoe 44 in its lowermost position, continued rotation of the drive shaft causes continuous repetitions of the described cycles, and, of course, as the angular velocity of the cam increases, centrifugal force comes more and more into play in a manner to throw the cam outwardly towards its position of maximum eccentricity during periods it is free so to move.

Since, when cam 34 is projected from the position of Fig. to that of Fig. 6, the center of symmetry A passes from one side to the other of the axis of rotation B, there will be a complete hammer stroke for each half revolution of the cam.

If control lever 5| be entirely released, spring 53 returns shoe 44 and hence cam 34 to the position of Fig. l, whereafter, since center A and axis B coincide, the disk, which has now lost its function as a cam or eccentric, will merely rotate idly and the stroking of the hammer will cease.

Of course, by applying different effective pressures to control lever 5l, an infinite number of hammer-stroke adjustments may be had, from the maximum full-stroke blow described above to a relatively light tapping. All adjustments within the entire range may be made without varying the angular velocity of the cam and thus without Varying the number of hammer blow per unit time.

In Fig. 'l shoe M is shown adjusted to a position to give a hammer stroke of about half maximum length, and the cam has been rotated to a position where it has just re-engaged roller il. It will be noted that arcuate shoe M is of suflicient angular extent to reduce the gap between roller lil and toe 4t sufficiently to prevent the cam being thrown by centrifugal force through that gap, which might otherwise effect a full hammer stroke in spite of the fact that shoe 1M is set for a partial stroke.

While I have shown and described a preferred embodiment of my invention, it will be understood various changes in design, structure and arrangement may be made without departing from the spirit and scope of the appended claims.

I claim:

1. In a power hammer wherein there is a spring-urged hammer staff and a diametrically slotted round cam slidably mounted upon a flatsided rotary shaft and a lift roller carried by said hammer staff and positioned to contact said cam when the latter is centered on its shaft; a movably mounted shoe for limiting the eccentric displacement of said cam, a support rod` for said shoe, a spring encircling said support rod for urging said shoe in the direction of said rotary shaft, a stop for limiting the movement of said shoe to effect centering of the cam, a thrust rod cooperable with said shoe, and an intermediately pivoted hand lever operable upon said thrust rod for urging said shoe in opposition to the action of said spring to vary the eccentric displacement of said cam, whereby said cam may be rotated idly against said lifting roller until said hand lever is moved to effect eccentric positioning of said cam.

2. In a power hammer wherein there is a spring-urged hammer staff and a diametrically Slotted round cam slidably mounted upon a flatsided rotary shaft and a lift roller carried by said hammer staff and positioned to contact said cam when the latter is centered on its shaft; a movably mounted shoe for limiting the eccentric displacement of said cam, a support rod for said shoe, a spring encircling said support rod for urging said shoe in the direction of said rotary shaft, a stop for limiting the movement of said shoe to effect centering of the cam, a thrust rod cooperable with said shoe, and a hand lever operable upon said thrust rod for urging said shoe in opposition to the action of said spring to vary the ,eccentric displacement of said cam, whereby said cam may be rotated idly against said lifting roller until said hand lever is moved to effect eccentric positioning of said cam.

3. In a power hammer wherein there is a spring-urged hammer staff and a diametrically slotted round cam slidably mounted upon a fiatsided rotary shaft and a lift roller carried by said hammer staff and positioned to contact said cam when the latter is centered on its shaft; a movably mounted shoe for limiting the eccentric displacement of said cam, a spring for urging said shoe in the direction of said rotary shaft, a stop for limiting the movement of said shoe to effect centering of the cam, a thrust rod cooperable with said shoe, and a hand lever operable upon said thrust rod for urging said shoe in opposition to the action of said spring to vary the` eccentric displacement of said cam, whereby said cam may be rotated idly against said lifting roller until said hand lever is moved to effect eccentric positioning of said cam.

4. In a power hammer wherein there is a spring-urged hammer staff and a diametrically slotted round cam .slidably mounted upon a flatsided rotary shaft and a lift roller carried by said hammer staff and positioned to contact said cam when the latter is centered on its shaft; a movably mounted shoe for limiting the eccentric displacement of said cam, a support rod for said shoe, a spring encircling said support rod for urging said shoe in the direction of said rotary shaft, a stop for limiting the movement of said shoe to effect centering of the cam, and a hand lever for urging said shoe in opposition to the action of said spring to vary the eccentric displacement of said cam, whereby said cam may be rotated idly against said lifting roller until said hand lever is moved to effect eccentric positioning of said cam.

5. In a power hammer wherein there is a spring-urged hammer staff and a diametrically slotted round cam slidably mounted upon a flatsided rotary shaft and a lift roller carried by said hammer staff and positioned to contact said cam when the latter is centered on its shaft;

va movably mounted shoe having a toe for limiting the eccentric displacement of said cam, a spring urging said shoe in the direction of said rotary shaft, a stop for limiting the movement of said shoe to effect centering of the cam, and a hand lever for urging said shoe in opposition to the action of said spring to vary the eccentric displacement of said cam, whereby said cam may be rotated idly against said lifting roller until said hand lever is moved to effect eccentric positioning of said cam.

6. In a power hammer wherein there is a spring-urged hammer staff and a diametrically slotted round cam slidably mounted upon a flatsided rotary shaft and a lift roller carried by said hammer staff and positioned to contact said cam when the latter is centered on its shaft; a movably mounted shoe for limiting the eccentric displacement of said cam, a spring urging said shoe in the direction of said rotary shaft, a stop for limiting the movement of said shoe to effect centering of the cam, and a hand lever for urging said shoe in opposition to the action of said spring to vary the eccentric displacement of said cam, whereby said cam may be rotated idly against said lifting roller until said hand lever is moved to effect eccentric positioning of said cam.

DAVID V. ACKERMAN'. 

